One hundred and fifteen persons with asymptomatic Entamoeba histolytica or E. hartmanni infection, or both, were given metronidazole (750 mg three times daily for 5 days), tinidazole (1 g twice daily on 2 consecutive days), or a starch placebo. Three posttreatment stools were examined in the 2 weeks following initiation of treatment. Cysts of E. histolytica reappeared in the stools of 37% of 30 given metronidazole, 62% of 34 given tinidazole, and 70% of 31 given placebo. Cysts of E. hartmanni reappeared in the stools of 46% of 24 given metronidazole, 69% of 16 given tinidazole, and 90% of 10 given placebo. Rapid absorption and short duration of treatment make both drugs ineffective for the treatment of ameba carriers.

The prevalence rates and household distribution of seroreactivity to Trypanosoma cruzi by complement fixation (CF) and indirect immunofluorescent antibody methods were determined in a population of 1,087 persons living in a rural area endemic for Chagas' disease in northeast Brazil. There was a gradual rise in the rate of seropositivity to 60% by age 20. Between ages 20 and 55 the prevalence rate remained at about 60%, but declined thereafter. The decline in the older age groups was not accompanied by a fall in geometric mean titer, suggesting that the decline might better be explained by an increased mortality among those seropositive than by a decrease in CF reactivity associated with age. There was variation in the rates of seropositivity in children among the geographic subunits, but the rates among adults were fairly uniform. Household clustering of seropositivity was demonstrated when both household size and age distribution were taken into account. The presence of a seropositive child less than 5 years of age was a good indicator of a household with a high rate of seropositivity; screening for young seropositive children might be a useful tool to locate high risk households. Seropositive children in households where the mother was seropositive but the father seronegative were significantly younger than seropositive children in households where the father was seropositive but the mother seronegative even though the age distribution and the overall rate of seropositivity in both groups of children were similar; thus, conversion to seropositivity earlier in life in children of seropositive mothers may not be due solely to increased exposure, but may indicate that the immunologic response in such children differed from that of children from seronegative mothers.

The efficacy of oxantel pamoate (1,4,5,6-tetrahydro-2-[trans-3-hydroxystyryl]-1-methyl pyrimidine pamoate) was evaluated in 25 children with severe Trichuris infection. The presence of chronic dysentery and sigmoidoscopic demonstration of whipworms in the intestinal mucosa were the criteria for inclusion in the trial. Most of these patients had severe anemia, rectal prolapse, digital clubbing, hypoproteinemia, and growth retardation. There was a high incidence of concomitant parasitism with other intestinal helminths and with Entamoeba histolytica and Giardia lamblia. Sigmoidoscopic grading of Trichuris load and egg count in the feces were carried out prior to treatment and 2 days after each course of oxantel therapy. Oxantel was administered at a dose of 10 mg/kg body weight twice daily for a 3-day course. Satisfactory response, as judged by relief of dysentery and absence of whipworms from the mucosa at sigmoidoscopy, was achieved in 17 patients after the first course and in the remaining 8 patients after a second course of oxantel. The drug was well tolerated and no side effects were noted during or after treatment. It is concluded that oxantel is a safe and effective anthelmintic for severe clinical trichuriasis.

Children with severe Trichuris trichiura infection pose significant social, clinical, and therapeutic problems in Malaysia. Thirty such children were investigated, and mebendazole was found to be safe and effective in the treatment of severe trichuriasis but it had to be given for a longer period than currently recommended. A poor correlation was found between egg load and worm burden in these children. Direct visualization of the rectal and colonic mucosa was the most reliable method of assessing severity in untreated cases, and response to treatment. The eggs of Trichuris that had been exposed to mebendazole were morphologically altered and not viable when incubated. This may be of considerable epidemiological importance.

The effect of inoculum size and time on the distribution of Toxocara canis larvae in the mouse was investigated by recovering larvae from various body regions 7, 14, 28, and 56 days after administration of either 200, 600 or 1,000 infective eggs to groups of ten male mice. An analysis of variance of larval recoveries from the carcass, liver, brain and cardiopulmonary system suggests that inoculum size was a significant factor determining the proportional recovery for each of these sites. Length of infection was significant in relation to numbers of larvae in the anterior carcass, genitourinary system, brain and heart plus lungs, while length of infection and inoculum size acting in concert influenced the numbers of larvae recovered from the carcass, liver, brain, heart and lungs. Crowding effects, manifested as altered dispersion rates, were seen in the heavier infections.

Serum IgE concentrations of patients with paragonimiasis were determined by a radioimmunosorbent test. The mean concentration was 3,462.3 IU/ml in a group of 13 cases of paragonimiasis miyazakii in which patients showed clinical symptoms and/or positive immunological diagnostic tests, and 1,026.6 IU/ml in a control group of 13 individuals who had eaten uncooked freshwater crabs, Potamon dehaani, but had been found to be free from the infection. Moreover, the IgE level of the pleural exudates obtained from four patients with paragonimiasis miyazakii on the day of bleeding or within several days after was significantly higher than that of their sera, ranging between 4,200 IU/ml and 10,000 IU/ml. This was true also in a case of paragonimiasis westermani. Sera and pleural exudates of patients with both forms of paragonimiasis were applied to immunosorbent columns of Sepharose 4B beads coupled with saline extracts of Paragonimus miyazakii, P. westermani, or P. ohirai. IgE eluted from the corresponding column was considered to be specific, being around 5% to 10% of the total IgE.

Schistosomiasis may be increasing in West Africa due to the development of water-resource projects which were given a strong impetus by the disastrous Sahelian drought. This report concerns the existing epidemiology of schistosomiasis in West Africa for the Fourth Region of Mauritania, along the Gorgol River. In this area two reservoirs are proposed, to supply a new rice irrigation system. During May and November 1974, field surveys were made to determine the prevalence and intensity of schistosomiasis, and the relevant species of snails. The surveys were made as a basis for designing the irrigation systems to minimize transmission. The only snails found in the area were two species of Bulinus; therefore, the human population was tested for Schistosoma haematobium. A high prevalence of schistosomiasis was found in M'Bout, the town nearest the proposed reservoir at Foum Gleita. Prevalence rates were lowest in Kaedi near the confluence of the Gorgol and Senegal rivers. During the period between the first and second survey the incidence rate among children in M'Bout became very high (68%), probably because of increased water contact related to the rains that broke the long drought in August 1974.

Calcific eggs of Schistosoma haematobium were separated from an inactive sandy patch in a cystectomy specimen from an Egyptian farmer; the purified egg suspension was injected into tail veins of inbred mice, some of which were killed immediately and some at intervals of 1, 2, 11, 14, 30, 90, 120, 180, and 365 days. Lungs were examined by tissue digestion and histologic analysis. Calcific egg burdens decayed in an exponential manner (eggs/g of lung tissue = 284.9e-0.001x where e = natural log and x = time in days), with a loss of 5,610 eggs/g of lung tissue, i.e., 98% reduction over the year of the experiment. Histologic examination revealed that calcific S. haematobium eggs incited a typical granulomatous reaction as they decalcified. Compared with viable egg granulomata, the response to calcific eggs was accelerated in onset, of lesser magnitude but persisted longer. Small numbers of calcific eggs persisted for at least 1 year after injection of either viable or calcific eggs. It is concluded that despite the apparent lack of tissue reaction to calcific eggs in chronic bladder lesions, these eggs are not antigenically exhausted foreign bodies. Moreover, it is shown that calcific eggs are degraded in significant numbers by mammalian tissue.

Clinical trials of hycanthone (single intramuscular dose) were undertaken in schistosomiasis mansoni patients in St. Lucia at five dose levels: 3.0, 2.5, 2.0, 1.5, and 1.0 mg/kg body weight. The most common side effect, vomiting, decreased in frequency from 51% at the highest dose to 3% at the lowest; minor side effects showed a similar trend. Three fecal specimens were examined before and at 6 months after treatment by qualitative, quantitative, and hatching techniques. All dose levels caused reductions in egg excretion of 89 to 98%. Rates of cure (absence of eggs by all three methods) according to dose (descending), pretreatment egg output (0–19, 20–49, 50–399, 400+ eggs/ml feces), and age (0–7, 8–14, 15–29, 30+ years) were analyzed to estimate the effect of each variable if the others had been constant. For dose, the standardized percentage success rates were 53.9%, 62.0%, 51.2%, 54.0%, and 27.4%; for egg output, 67.0%, 51.8%, 43.2%, and 21.7%; and for age, 25.2%, 34.5%, 59.3%, and 57.4%. Logit regression analysis shows a significant difference in cure rate (a) between the lowest dose and all others, among which latter there was no difference, (b) between patients excreting 0 to 49 eggs/ml before treatment and those excreting 50+ eggs/ml, and (c) between the age groups 0 to 14 and 15+ years. All dose levels caused some regression in enlargement of liver or spleen. A dose of 1.5 to 2.0 mg/kg body weight is considered to be as effective as one of 3.0 mg/kg and more acceptable for a control program because of the marked reduction in side effects.

Groups of young hamsters were exposed to 3, 20, 40, 80, or 160 cercariae. A highly significant correlation was observed between the number of cercariae, worm burdens, and liver and fecal egg counts. The most heavily infected animals were the first to lose weight and die. Hamsters exposed to 20 or more cercariae and harboring a mean of 4.2 or more worm pairs developed significant hepatosplenic disease by 10 weeks after infection as assessed by hepatomegaly, splenomegaly and the development of portal hypertension. Lightly infected animals with single worm pairs did not develop significant disease.

Anti-liver antibody has been demonstrated in the sera of Schistosoma japonicum-infected rabbits. By the 8th week after exposure to cercariae, perceptible levels of autoantibody were present and appeared to be directed predominantly against determinants located in the cell membrane of the hepatocyte.

In a study of 662 sera from a hydatidosis endemic area, the indirect hemagglutination test based on a minimal nonspecificity criterion of positivity and the latex agglutination (LA) test were found to be suitable screening techniques for the detection of sera positive to the arc 5, diagnostic of hydatid infection. The lower nonspecificity of the LA test, its greater simplicity and its excellent correlation with the immunoelectrophoresis test suggest that it is the choice screening technique for use in field surveys or seroepidemiologic studies of hydatid disease. The advantages and limitations of this serologic approach for the detection of human hydatid cyst carriers in field studies are discussed.

Methicillin resistant staphylococci are unevenly distributed throughout the world; the explanation for this is not known. During a survey of local hospitals for methicillin resistance, a number of strains from South Vietnam became available for study. Tests were performed in microtiter plates using various concentrations of several antibiotics with a final concentration of organisms of 105/ml and 108/ml. With the larger number of organisms in the inoculum, 17% of strains required 12.5 µg/ml or more of methicillin for inhibition. This is in contrast to a very low percentage of methicillin resistant staphylococci from local sources encountered in our laboratory. An unexpected finding was the occurrence of considerable lincomycin resistance in staphylococci from South Vietnam.

An 11-year-old boy developed axillary bubonic plague and plague meningitis 3 days after skinning a dead coyote near Albuquerque, New Mexico. The coyote carcass was recovered 10 days later, and Yersinia pestis was isolated from spleen and marrow of the animal. This is the first report of human plague from exposure to a coyote. A review of experimental and epidemiologic studies suggests that severe plague infection in members of the family Canidae is unusual, and that the risk of acquiring plague from direct contact with coyote tissues is minimal. Nevertheless, certain precautions are outlined for persons working with wild coyotes.

Pathogenic Mycobacterium ulcerans were recovered from the stool of anole lizards up to 11 days after inoculation by stomach tube. M. ulcerans was isolated from the liver of 3 of 20 lizards and acid fast bacteria were seen in the mucosa of intrahepatic bile ducts in 2 of these 10 weeks post-inoculation. These results provide equivocal support for our hypothesis that herpetofauna are a reservoir of infection with M. ulcerans.

In a controlled study in Ghana, the hemoglobin electrophoretic pattern in 112 patients with Burkítt's lymphoma was compared to that of their nearest neighbor controls of the same age, sex, and tribe, as well as their sibling controls. Analysis of the data obtained did not show any statistically significant protective advantage for sickle cell trait against Burkitt's lymphoma. Hemoglobin C trait appeared to offer a slight protective advantage (p < 0.1), but this did not reach statistical significance. These results do not disprove the malaria co-factor hypothesis in the etiology of Burkitt's lymphoma, but deprive it of an additional indirect evidence in its favor.

Between July 1973 and December 1974, 304 autopsies were done at Hopital Mama Yemo, Kinshasa, Republic of Zaire. The causes of death and sudden death were tabulated and analyzed. The frequency of various diseases and groups of diseases among all the individuals and a large subset of individuals who died traumatically are tabulated and discussed. The present report is the most quantitative, albeit only, current estimate of mortality and prevalence of diseases in Zaire.

Stable traps, each baited with a jackrabbit and either a chicken or a pheasant, collected more than 21,000 mosquitoes in the Sacramento Valley, California, in 1972 and 1973. The focus of interest was the feeding behavior of Culex tarsalis, a primary vector of encephalitis viruses. Generally, feeding success was less and feeding rates on the jackrabbit were greater when larger numbers of mosquitoes were collected, or when a bird was exposed that was less receptive to mosquito feeding. Greater feeding rates on the jackrabbit apparently resulted from decreased feeding on the avian host and from diversion of mosquitoes to the jackrabbit. Figures are given that show how changes in feeding rates on birds affect the probabilities that a mosquito that feeds twice would feed both times on a bird, or on a bird and then on a mammal. Relatively small collections of nine mosquito species other than C. tarsalis revealed distinct species differences in feeding behavior. Aedes melanimon showed a preference for jackrabbit, which is relevant to its role as a vector of western equine encephalitis and California encephalitis viruses.

An informal workshop designed to explore recent advances in the immunology of schistosomiasis was held on 12 November 1975, in conjunction with the meetings of the American Society of Tropical Medicine and Hygiene and American Society of Parasitologists. This workshop was dedicated to the memory of Dr. Elvio H. Sadun, providing an open forum for the presentation of recent advances in, and definition of areas of critical concern for, the immunologic study of Schistosoma mansoni. The following report represents a brief synopsis of this meeting.

The workshop was originally suggested during the meeting in Bellagio, which was sponsored by the Rockefeller Foundation. Scientists at the meeting were invited to participate in this workshop and mold its format. In this report, the inclusion of certain investigators and exclusion of others simply reflects the voluntary nature of the workshop.